The invention relates to a suction air nozzle for a textile machine for storing a yarn length of a running yarn passing the nozzle opening.
Suction air nozzles of this type have been known for a long time in conjunction with spinning machines or winding machines or the service units associated with these textile machines and are described in numerous patent applications.
Suction air nozzles of this type are used, for example, to keep the yarn tension constant during the winding operation or are used, for example, in spinning machines to store the temporarily occurring yarn excess when running the workstations up to operating speed and to supply it successively to the winding device of the relevant workstation.
A textile machine is described in German Patent Publication DE-OS 1 785 321, in which a suction air nozzle is positioned in the yarn running direction shortly before the winding device, right next to the regular yarn running path. The suction air nozzle has, in the region of its inlet opening, an upper and a lower deflection roller, in each case, and pneumatically loads the running yarn in such a way that a yarn loop reaching into the suction air nozzle is formed between the deflection rollers. In other words, the suction air nozzle ensures that the yarn is always wound at a sufficiently great yarn tension onto a winding device.
German Patent Publication DE 40 27 210 A1 describes an air spinning machine, the workstations of which are supplied by an automatically operating service unit.
Both the moveable service unit and the workstations of the air spinning machine are in each case equipped with suction air nozzles. As already mentioned, the yarn excess occurring when workstations of this type are run up to operating speed is to be temporarily intermediately stored by means of the suction air nozzle arranged in the region of the workstations.
A similar suction air nozzle for temporarily receiving a relatively large quantity of yarn is also described in German Patent Publication DE-AS 22 21 316 using the example of an open-end spinning machine, or in European Patent Publication EP 1 207 225 A2, which shows the use of a suction air nozzle of this type on an air spinning machine.
The suction air nozzles described in the aforementioned literature references generally have inlet openings, which have their greatest extension in the yarn running direction, with, as can be seen, for example, from German Patent Publication DE-OS 1 785 321 or European Patent Publication EP 1 207 225 A2, the height of the inlet opening clearly exceeding its width. In these known suction air nozzles, the clear cross section of the nozzle body, which substantially corresponds to the size and shape of the inlet opening, is constant from the inlet opening to an outlet opening in the region of a suction air connection.
The disadvantage in these known suction air nozzles is not only their lack of suction force, but, in these suction air nozzles, there is always the risk, despite an elongate cross section in the yarn running direction that the sucked-in yarn loop may become twisted or form knots which may appreciably disturb the operation of the workstations.
It has therefore already been proposed to modify the shape of such suction air nozzles or the clear cross section of suction air nozzles of this type in such a way that the risk of knot formation is reduced.
German Patent Publication DE 28 02 913 A1 describes, for example, a suction air nozzle, the nozzle body of which has a constriction on its entire length, by means of which its clear cross sectional area is divided into two partial areas. The diameter of the suction air nozzle is thus only about half as large in the region of the constriction as in the region of the two partial areas.
Furthermore, suction air nozzles are known from German Patent Publication DE 38 29 151 A1, the nozzle bodies of which are curved in the axial direction. The clear cross sectional face also has lateral partial faces here, in which the yarn strands of a yarn loop which has been sucked in are to be deposited in a defined manner.
It was possible to slightly ameliorate the problem of knot formation in the case of long yarn loops by means of suction air nozzles, such as are known from German Patent Publications DE 28 02 913 A1 or DE 38 29 151 A1, but suction air nozzles of this type continue to have the disadvantage that, in particular long yarn loops inside the suction air nozzle are not adequately reliably tensioned because of lack of suction force or inadequate suction force distribution.